NAME

Crypt::AuthEnc::OCB - Authenticated encryption in OCBv3 mode

SYNOPSIS

 ### OO interface
 use Crypt::AuthEnc::OCB;
 # encrypt and authenticate
 my $ae = Crypt::AuthEnc::OCB->new("AES", $key, $nonce, $tag_len);
 $ae->adata_add('additional_authenticated_data1');
 $ae->adata_add('additional_authenticated_data2');
 my $ct = $ae->encrypt_add('data1');
 $ct .= $ae->encrypt_add('data2');
 $ct .= $ae->encrypt_add('data3');
 $ct .= $ae->encrypt_last('rest of data');
 my $tag = $ae->encrypt_done();
 # decrypt and verify
 my $ae = Crypt::AuthEnc::OCB->new("AES", $key, $nonce, $tag_len);
 $ae->adata_add('additional_authenticated_data1');
 $ae->adata_add('additional_authenticated_data2');
 my $pt = $ae->decrypt_add('ciphertext1');
 $pt .= $ae->decrypt_add('ciphertext2');
 $pt .= $ae->decrypt_add('ciphertext3');
 $pt .= $ae->decrypt_last('rest of data');
 my $tag = $ae->decrypt_done();
 die "decrypt failed" unless $tag eq $expected_tag;
 #or
 my $result = $ae->decrypt_done($expected_tag); # 0 or 1
 ### functional interface
 use Crypt::AuthEnc::OCB qw(ocb_encrypt_authenticate ocb_decrypt_verify);
 my ($ciphertext, $tag) = ocb_encrypt_authenticate('AES', $key, $nonce, $adata, $tag_len, $plaintext);
 my $plaintext = ocb_decrypt_verify('AES', $key, $nonce, $adata, $ciphertext, $tag);

DESCRIPTION

This module implements OCB v3 according to <https://tools.ietf.org/html/rfc7253>

EXPORT

Nothing is exported by default.

You can export selected functions:

  use Crypt::AuthEnc::OCB qw(ocb_encrypt_authenticate ocb_decrypt_verify);

FUNCTIONS

 my ($ciphertext, $tag) = ocb_encrypt_authenticate($cipher, $key, $nonce, $adata, $tag_len, $plaintext);
 # $cipher .. 'AES' or name of any other cipher with 16-byte block len
 # $key ..... AES key of proper length (128/192/256bits)
 # $nonce ... unique nonce/salt (no need to keep it secret)
 # $adata ... additional authenticated data
 # $tag_len . required length of output tag

  my $plaintext = ocb_decrypt_verify($cipher, $key, $nonce, $adata, $ciphertext, $tag);
  # on error returns undef

METHODS

 my $ae = Crypt::AuthEnc::OCB->new($cipher, $key, $nonce, $tag_len);
 # $cipher .. 'AES' or name of any other cipher with 16-byte block len
 # $key ..... AES key of proper length (128/192/256bits)
 # $nonce ... unique nonce/salt (no need to keep it secret)
 # $tag_len . required length of output tag

 $ae->adata_add($adata);                        #can be called multiple times

 $ciphertext = $ae->encrypt_add($data);         # can be called multiple times
 #BEWARE: size of $data has to be multiple of blocklen (16 for AES)

 $ciphertext = $ae->encrypt_last($data);

 $tag = $ae->encrypt_done();                    # returns $tag value

 $plaintext = $ae->decrypt_add($ciphertext);    # can be called multiple times
 #BEWARE: size of $ciphertext has to be multiple of blocklen (16 for AES)

 $plaintext = $ae->decrypt_last($data);

 my $tag = $ae->decrypt_done;           # returns $tag value
 #or
 my $result = $ae->decrypt_done($tag);  # returns 1 (success) or 0 (failure)

 my $ae_new = $ae->clone;

SEE ALSO

• CryptX, Crypt::AuthEnc::CCM, Crypt::AuthEnc::GCM, Crypt::AuthEnc::EAX
• <https://en.wikipedia.org/wiki/OCB_mode>
• <https://tools.ietf.org/html/rfc7253>